1. Field of the Invention
This invention relates to resorcinol-based epoxy resins having improved physical and mechanical properties such as a reduced ability to absorb moisture, high glass transition temperature, good processability and less volatility.
2. Brief Description of the Prior Art
Epoxy resins are a class of thermoset resins with a wide range of applications. For example, epoxy resins are employed in composite fabrication in both wet and dry lay-up techniques well known to those skilled in the art for the electrical, aerospace, filament winding and hardware industries. The disadvantage of many epoxy resins is their ability to absorb high amounts of moisture when they are used in both wet and dry composite fabrication. Obtaining an epoxy resin having a low moisture absorption characteristic, however, in many cases, has led to a compromise in other desirable physical and mechanical properties such as, for example, high glass transition temperature, ease of processability, flexural properties, tensile properties and curing conditions.
It is well known that all epoxy resins contain the epoxide, orirane or ethoxylene group: ##STR3## wherein X represents the point of attachment to the remainder of the resin molecule. The epoxide function generally appears in the form: ##STR4## known by those skilled in the art as the glycidyl group which is attached to the remainder of a compound by such as, for example, an oxygen (i.e., glycidyl ether), nitrogen (i.e., glycidyl amine), or carboxyl group (i.e., glycidyl ester).
U.S. Pat. No. 2,892,849 discloses a process for preparing epoxyalkyl aryl ethers, including resorcinol diglycidyl ether.
U.S. Pat. No. 4,916,202 discloses an epoxy resin having glycidyl amine groups. This patent discloses epoxy resins made from aliphatic amines, sulfonamides, and aromatic amines.
Japanese Patent No. -026173 discloses a process for making an epoxy resin from a carboxylic acid derivative of resorcinol such as Beta-resorcylic acid.
Japanese Patent No. -020172 discloses the process of making an epoxy resin from the reaction of another resorcinol derivative namely 4,4'-thiodiresorcinol with the epichlorohydrin.
U.S. Pat. No. 2,467,171 discloses stereoisomeric 1,3-diglycidyloxybenzenes which have been known for many years.
Industrial and Engineering Chemistry, Volume 52, No. 4, Apr. 1960, pp. 324-325 discloses epoxy resins from resorcinol-acetone condensation products.
U.S. Pat. No. 3,291,837 discloses the preparation of monoepoxy compounds from benzyol resorcinol and thier application towards U.V. stabilizers.
U.S. Pat. No. 4,656,207 discloses resorcinol-based epoxy compounds but not benzoyl resorcinol diglycidyl ether compounds.
None of the prior art discloses the preparation and application of diglycidyl ether derivatives of benzyol resorcinol, styryl- and alphamethyl styryl substituted resorcinol and also the tetraglycidyl ether of bis[resorcinol] type resin of the present invention.
In spite of these prior art disclosures, there remains a very real and substantial need for a resorcinol-based epoxy resin having enhanced curing properties, flexural properties, tensile properties, low moisture absorption properties, a high glass transition temperature and less volatility.